Formulation of ascorbic acid microemulsions with alkyl polyglycosides.

Ascorbic acid microemulsions for topical application were developed. In this study, microemulsions were prepared using HLD (hydrophilic lipophilic deviation) concept to optimise the formulation. From this optimal formulation, the realisation of dilution ternary diagrams leads to obtain microemulsion zones. In addition, the effects of composition variable on the physicochemical characteristics of each system were investigated. After optimisation of the microemulsion systems, ascorbic acid was loaded in the formulations. Surface tension and small angle neutron scattering were used to characterise the surface properties and the structure of the microemulsions. Bicontinuous structure microemulsions were identified, and the influence of ascorbic acid localisation at the interface leading to modifications of the microemulsion structure was pointed out. The solubilisation of ascorbic acid, the stabilisation and in vitro transdermal penetration "Frantz cells" of ascorbic acid microemulsions were studied. Three different microemulsions were envisaged. The results confirmed that these microemulsion systems present a real interest for formulation and protection of ascorbic acid. Regarding their transcutaneous penetration behaviour, the different microemulsions studied could be useful for different topical applications. A major location of ascorbic acid found in the epidermis where the decomposition of melanin occurred indicates that microemulsion could be considered as a suitable carrier system for application of ascorbic acid as a whitening agent. In addition, a good passage of the drug in the dermis could be interesting for the relative oxygen matrix damage.